Means for forming zones of varying and variable strengths in magnetic fields.



A. F. JOBKEL.

MEANS FOR FORMING ZONES 0F VARYING AND VARIABLE STRENGTHS IN MAGNETICFIELDS.

APPLICATION FILED JAN. 24, 1912.

Patented Mar. 16, 1915.

' INVENTOR HucFsT -O WITNESSES ATTORNEYS net fields of gaps.

UNITED STATES PATENT OFFICE. I

AUGUST 1'. JOB, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOB OF ONE-HALF TOIon G. BURNS, DANIEL BINGHAM, KATHERINE CRUMAY, THOMAS HIGGINS, AND H.P. aazzm, ALL OF PITTSBURGH, PENNSYLVANIA.

mus FOBIOBIING ZONES OE VABYING All?) VARIABLE STRENGTHS IN MAGNETICFIELD Specification of Letters Patent.

Patented Mar. 16, 1915.

'lpplicatlon fled January 24, 1912. Serial No. 673,131.

To all whom it may concern:

Be it known that I, AUGUST F. JOBKE, a' citizen of the United States ofAmerica, residing at Wilkinsburg, in the county of Allegheny and Stateof Pennsylvania, have invented certain new and useful improvements Meansfor Forming Zones of Varying an Variable Strengths in Magnetic Fields,(Case 1,) 'of which the following is a specification, reference beinghad therein to the accompanying drawing.

My invention rclates'to improvements in means for forming zones ofvarying and variable strengths in magnetic fields, relatingmore'particularly to the formation of the magnet poles which produce themag- So far as I am aware, the only attempts which have been made tovary the field strength of a magnetic gap have embodied the idea ofchanging the distances between the pole pieces which form the ap, thisdifference or variation being provifed either b adjusting one or most ofthe pole pieces in directions toward and from each other,

7 by employing pole pieces adapted to divide the ma etic field intoseveral fields each of the divided poles occupying a position toincrease or diminish the distance between the two poles from each of theother divided poles, or to employ this latter idea with each of thedivided poles adjustable to permit of variations in such distance.

Any arrangement which involves a change in the distance between opposingoles of a gap is disadvantageous for the ollowing reasons: Assuming, forexample, the rovision of two opposing pole pieces, one involving astructure havinga plane flat, surface or face, with the other in theform of a'plurality of wedges, the ed s of the wedge form being spaoedatdi erent distances from the flat face of the other pole, an example ofwhich is shown in Figure 6 of the drawing, and to which reference may behad in connection with this discussion,

the showing therein made providing for three zones of varying strength.It should be noted that this particular form represents approximatelythe greatest value heretofore known in this special type of apparatus.As will be seen by reference to -posing poles, the advantage gained bysaid figure, the zone of greatest strength is that provided by the edgein closest proximlty to the opposite pole piece, while that on theright, being the greatest distance from the opposite pole piece providesthe zone of least strength, the intermediate zone having a strengthbetween the outer zones. As will be seen, each zone has its lines offorce converging from the'flat pole face to the opposing edge, with theface occupied by each zone on the fiat face approximately the samewidth. As will be seen by the lines connecting the opposite poles, thefield of greatest strength, has in accordance with the well knownphysical law that the greater I its, the greater will be the magneticattraption, it being understood that where an angle of convergence isunduly increased, as by decreasing the distance between the opincreasein the angle of convergence will be overcome by an increase in strayflux, so that a loss in flux is provided with a resultant waste. On thecontrary, however.

where the angle of convergence is decreased,

as by increasing the distance between the poles, the field is not onlyweakened in strength, but in addition, the lines of force will provide adifl'erent form ofrfield, the lines bulging owing to the re ellentaction of similar polarity, the lines 0 force closely approaching exactparallelism and of almost uniform density, with a consequent result thatthere is no pull or attraction in either direction on a planeintersecting at right angles and centrally the space between twoopposing poles, each of which is wedgeshaped with the edges inopposition to each other, such plane corresponding to the flat face ofthe lower pole in said figure, this attraction increasing from zero onthat face to its maximum at the pole edge; where a structure of thistype is used in magnetic ore separation, it will be readily un erstoodthat where the distance betweel. the poles is increased in this manner te may result a condition where a strong 11 x will be provided butwithout any or but very little pull or attraction of ore particles nearthe flat face, thereby providing for but a very small efiiciency in thefield. To decrease the strength of such field by increasing the distancewould not only affect the particular gap in question, but also the othergaps or zones, in addition to requiring the employment of greater power.And where the zones are variable, as by adjustment of the pole pieces,toward each other as where for instance, the parts are carried by arotating carrier, adjustment of any or all of the edges couldonly be hadwhen the apparatus is at rest, so that where the structure is employedfor magnetic,ore separation, adjustments can be had only under such restcondition; where, therefore, proper adjustment can only be obtained bytesting the ore material passing through the zones it will be obviousthat there is a large amount of time wasted due to the requiredstoppages of apparatus where the adjustment is not 'had at once.

My present invention aims to not only overcome the objectionablefeatures indicated above, but in addition to increase the efliciency ofapparatus employing magnetic fields by making them more flexible andcapable of uses heretofore not possible. For

tance. 1 am able to produce the results tion is employed in connectionwith magnetic ore separators: (1) The division of the field of a magnetpole into zones of difierent strengths for the separation of materials"of different permeability from each other. (2) The adjustmentofdifferent zones in the same field without altering the distancebetween opposed poles. (3) The adjustment of different zones in the samefield by varying the reluctance of the individual paths. (4 Apredetermination of the ratio of the different zones to one another.These may be considered as a few of the objects of the presentinvention.

Therefore, to these and other ends, the nature of which will be readilyunderstood as the invention is hereinafter disclosed, my inventionconsists ,in the improved construction and combination of partshereinafter fully described, illustrated in the accompanying drawingsand particularly pointed out "in the appended claims.

In' the accompanying drawings, in which similar reference charactersindicate similar parts in each of the viewsFig. 1 is a fragmentary view,partly in section, showing a magnetic field divided irhtozones, with.the upper pole in the form of a secondary magnet, the field being shownas provided with'three zones of different strengths. Fig. 2 is a similarview showing a modification of the idea, ,four zones being provided,both pole pieces being arranged in accordance withiny invention. Fig. 3is a similar view, also. showing four zones and illustrating a indicatedby the following, where the inven- .and'14' are secured to secondarymagnet, the lower pole piece being shown as extending axially of avertical magnet. Fig. 4 is a similar view, showing a differentarrangement of the means for varying the strength of the gaps. Fig. 5 isa similar view, showing both pole pieces formed in accordance with myinvention, this particular type providing for the greatest variance ingap strengths. Fig. 6 is a similar view illustrating a known form of 6structure for producing the result. Fig. 7 is a view of a still furthermodification of my idea, the view also having illustrations for thepurpose of showing comparisons with Fig. 6.

In a magnetic circuit having a constant magneto-motive force, the fluxdensity depends on the total reluctance of the circuit traversed, everyair gap representing a large reluctance relative to aniron-cireuitroportional to the length of the gap; 0 vionsly, therefore, variationsin the length of the air gaps affect the flux density therein. Asheretofore pointed out, however, variations in density provided bychanging the length of the air gap between the poles, isdisadvantageous, some of the reasons for which being heretofore setforth. To avoid these objections, I provide for retainingthe air gaps ina constant length by introducing an additional reluctance in the circuitat any point independent of such gap for the purpose of reducing theflux to the desired strength, on the principle that a. magnetic circuitcan be shunted by an additional ath we of different reluctance,producing a stronger main path and weaker shunt-path and rendering itpossible to provide more than one separatmg-gap. It is 01 1 thisprinciple that base my invntion, and for convenience, I placeallshunt-paths in the pole shoe of one or both "poles; in this manner,the shuntpaths are as short as possible and avoid a leakage of flux.This idea can be provided in many forms, a few of which are indicated inthe drawings. For the purpose of explaining the invention, I will use,for example, the showing of Fig. 1, in which 10 represents a horizontalmagnet with a vertically rising pole shoe 11 opposing an edge of asecondary magnet 12 located thereabove, Additional magnetic features ormembers 13 the shoe 11, as by bolting, these magnetic members beingspaced from thefs hoe 11 and from each other, being in opposition toopposing edgesof the magnet -12, this form disclosing a structureproviding three difl'erent zones, a-versin which, for the purpose of illtration, haveshown a conveyer 16 such aslwouldbe provided in connectionwith magnetic ore separators. For convenience in interpreting theinvention, I .have shown the several 2'. poles 11, 13, and 14 asseparated by insulation 15. This, however, is simply for the 13 theinsulation of the electrical art beingunknown, so far as I am aware, inmagnetic circuits. The insulation is intended to represent a suitablereluctance, whose permeability is unity, and this reluctance can beprovided in any desired manner.

It should be noted, that in a preferred form of my invention, the boltsby means of which the magnetic members 13 and It are secured to the poleshoe 11 arelof -nonmagnetic material in order that aiiiron-circuitbetween these separated members is prevented, excepting under conditionspresently described. i

As will .be readily understood, in this construction there are providedthree paths for the flux to travel, the first being that between theshoe 11 and the opposing edge, this zone being of the greatest strengthby reason of the fact that there is provided the smallest reluctance ofthecircuit, vi.'z., the length of the gap between opposing poles; thesecond path is that provided between the member l3 and its opposing poleface of the secondary magnet 12; in this zone, the same amount ofreluctance is provided in the separating gap (the space between theopposing poles) and additionally the reluctance provided by the spacingbetween the pole shoeell and the member L3, this increase in reluctanceacting to decrease the strength of the zone. in question, without,however, art: footing the angle of convergence. of the lines of forceinthe field or gap. The third zone provided bietweefn Ithe meraiaber 14and hits 0. posie gee t esecon ry magnet as itg streii gth decreasedfrom both of theother zones by reason of the fact that the flux pathtraverses both reluctance gaps 15 as well as the field gap. From theabove, it will be seen that in each zone, the distance between the oping pole faces is the some, providing simi ar angles of convergence inconnection with each zone, as shown, for in stance, in 7, the zones,however, being oi diflerent strength with that of the pole shoe 11 whichis integral with the magnet core, as the maximum, the zones decreasinginstrength-proportionately to the amount of additional reluctance providedwithin the circuits. Obviously, the strength of the several zones can bereadily determined by knowing the section. of the reluctance gapsbetween the separated members. However, the strength 0 any auxiliaryzonecan be readily increased without afiecting the distance between theopposing poles of the fields by providing an iron-path between themembers. This path may be formed in any suitable manner, any magneticmaterial bein; mpioyed and. b controlling the cram"- section. of theincrease instrength can be readily controlled. For the p ose, themagnetic material may be in the orm of blocks, sheets, or even wires,the purpose being to provide a path of less reluctance than thereluctance gaps, through which path the flux flows more readily and thusincreases .the st h of the circuit passing through the members. In Fig.1 I have shown a member of thistype at 18. As will beobvious thestrength ad ust'rng operation providiad by the member 18 can take placewithout afllecting the operation of the rator; and it will also beobvious that it will only be necessary to change the cross-sectionalarea of such member to vary the stnength, so that variations can be madefor testing purposes while the ppa-ratns is in operation and properstrengt to produce the best results quickly obtained.

As will be obvious, this idea may be em- ?oyed in various forms ofconstruction.

or instance, in Fig. 2 the secondary magnet is replaced by a similarconstruction to that shown at the bottom, the auxiliary members being ofdifferent cross-sectional size and obviously providing for a difi'erentcross-section of the reluctance gap. 1 This particular constructionprovides a greater variance in zone st engt than in the form shew-n. inFig. L n this form, each zone beyond the inner one represented by theshoe 11 is subjected to, the reluctance of two spaces instead of but oneas in the structure of F ig. 1, and in addition, the successive membersand the spaces therebetween formmg the reluctance gaps are reduced byshortening thereby increasing the reluctance for the individual shuntcircuit; in this figure I also show the application of the members 18for the the zone strength.

In Fig. 3 I show a somewhat similar arrangement' in connection with amagnet havmg a vertical axis, the opposing pole being provided by asecondary magnet, as in Fig. 1. In this form, as in Fig. 2, the membersare of .succesmwely decreased length to increase the reluctance. In thisform, a slightly dillerentapplication of the bridg 111%. 18 1s shown,illustrating an- 0t er way in which the adjustment in the zone strengthmay be accurately made.

In Fig. 4, a diiferent arrangement of the sameddea. is provided, thisarri ment givmg a smaller ratio at strength tween the strongest zone andthe next than the second and third one, on account of the diflerentratio of .reluctances between them. This arrangement may also beadvantageously employed reason of the ability to-provide for fineradiustments infield strength, the dotted lines in the re-showin adifierent way in which the bridging mem rs may be purpose of adjusting),

employed, each of the auxiliary members being shown as magneticallyconnected to the pole member 11.

In Fig. 5 I show an arrangement which permits of an extreme differencein strength of the several zones, the reluctance between the same beingincreased to approximately their largest values. In this form, the shaes of the auxiliary members or poles is made so that their faces retaintheir most advantageous form, while the material in rear of the faces iscut awa to increase the reluctance of the spaces, t us -a highefficiency is insured for every one of the gaps at their greatestdifierence in strength. This form is probably of the greatest advantage,by reason 0 the fact that it affords the maximum range, and by the useof bridge memberscan be readily adjusted to increase the strength of thezones, it be ing understood, of course, that this arrangement does notprovide for a decrease in the zone strength excepting by affecting thestrength of the entire magnet as by reducing the number of ampere-turns.

Fig. 7 shows still another form in which this operation can be provided,this view being presented more particularly as showing one way, in whichto comfiare the efi'ect to the effect produced by a di erent type ofapparatus.

From the above, it will be readily understood that in'each type, thelength of the gapsis the same for each of the zones of any particularfield; consequently, as shown in Fig. 7, the angles of convergence aresimilar in each zone, the only difference bemg in the zonal strength.Where a structure of this type is employed in magnetic ore separation,each zone becomes a separating (gap and the ore conveyer intersects atsubstantiall the same distances from the poles in eac zone. Obviously,since the angles of convergence are the same in all of the zones theaction of the circuits will be the same in each zone excepting for thestrength of the zone, and as this strength is controllable as indicated,it will be obvious that a cI ean-cut separation will be provided. 1

While my invention is primarily intended. for use in connection withmagnetic ore separation, and I have. disclosesd it mainly in connectionwith such use, I believe the invention-to be of broaderscope andsuitable for other purposes, however, and I therefore desire it to beunderstood that no specific application which may h ve been herein madeshall be held toexclu e other applications of the same general ideaembodied herein, the structural and operative characteristics of whichare the equlvalents "of those herein set forth, even though suchapparatus may be utilized "in different relations o fiect a specificallydifferent result.

reluctance of the magnetic circuit.

3. Means for formin zones of varying strengths in magnetic fields withsubstantially constant length of the zonal gap and including a fieldpole element having a mem: ber cooperating to provide a maximum zonestren h and a magnetic member spaced there rom to increase thereluctance of the circuit through the second member.

4. Means for formin zones of varying strengths in magnetic elds withsubstantially constant length of the zonal gap and includin a field poleelement having a plurality 0 members, the faces of which are positionedto cofiperate in roviding'separate gaps of equal length, t e membersbeing spaced apart to provide increasing re luctance to the magneticcircuit passing through the members.

5. Means for forming zones of varying strengths in magnetic elds withsubstantially constant length of the zonalgap and includin a field poleelement having a plurality 0 members, the faces of which are positionedto cooperate in providing separategaps of equal length, the membersbeing spaced apart to provide increasings reluctance to the magneticcircuit pa ing through the members, said members being normally" out ofmagnetic contact.

6. Means for forming1 zones of varying strengths in magnetic elds with"substantially constant length of the zonal gap and includin a fieldpole element having a p urality 0 members, the faces of which apositioned to cooperate 1n providing separategaps of equal, length, themembers being spaced apart provide increasing re-' luctance to themagnetic circuit passing through the members, said members beingnormally out of magnetic contact, and independent bridge members adaptedto connect two or more members magnetically to adjust the zone stren h.

8. In a magnetic eld, means for establishing a magnetic circuit with azonal g of substantially constant length, and mea s for varying thestrength of the gap independent of its length by varying the circuitreluctance.

9. In a magnetic field, means including opposing pole elements 'forestablishing a magnetic circuit with a plurality of zonal gaps, andmeans for varying the strength of the zones relatively to each other byaltering the reluctance between zones in a pole element.

10. In a magnetic field means including 20 opposing pole elements orestablishing a magnetic circuit with a plurality of zonal gaps, andmeans for varyin the strength of the zones relatively to eac other byaltering the reluctance between zones in each 26 of the pole elements.

In testimony whereof I aflix my signature in the presence of twowitnesses. 7

AUGUST F. J OBKE.

Witnesses:

MAX H. SBOLOVITZ, HORACE G. SEI'rz.

